Among the defense witnesses called to testify in the sexual assault trial of dermatologist Dr. Calvin Day Thursday was Christine Lewis, his former office manager.

Lewis said the two had an affair that began 12 years ago while she was employed by Day.

Lewis said the couple is currently living together in Boerne.

Lewis said they managed to keep their affair secret from the other 20 employees in the office even though she admitted having sex with Day during office hours in a secluded room at the rear of his office called the “Bat Room.”

Asked how often, Lewis said, “Weekly to monthly, possibly twice a week.”

During her testimony, Lewis was asked to compare photographs of Day’s male sexual anatomy to sketches and photographs identified during testimony earlier this week from the woman who has accused Day of sexually assaulting her in the Bat Cave in August 2010.

If he is found guilty of the assault, Day faces a maximum sentence of 20 years in prison.

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